Intercontinental comparison of optical atomic clocks through very long baseline interferometry

  • 1.

    McGrew, W. F. et al. Atomic clock performance enabling geodesy below the centimetre level. Nature 564, 87–90 (2018).

    ADS 

    Google Scholar
     

  • 2.

    Ushijima, I., Takamoto, M., Das, M., Ohkubo, T. & Katori, H. Cryogenic optical lattice clocks. Nat. Photon. 9, 185–189 (2015).

    ADS 

    Google Scholar
     

  • 3.

    Brewer, S. M. et al. 27Al+ quantum-logic clock with a systematic uncertainty below 10−18. Phys. Rev. Lett. 123, 033201 (2019).

    ADS 

    Google Scholar
     

  • 4.

    Wynands, R. & Weyers, S. Atomic fountain clocks. Metrologia 42, S64–S79 (2005).

    ADS 

    Google Scholar
     

  • 5.

    Panfilo, G. & Arias, F. The coordinated universal time (UTC). Metrologia 56, 042001 (2019).

    ADS 

    Google Scholar
     

  • 6.

    Riehle, F., Gill, P., Arias, F. & Robertsson, L. The CIPM list of recommended frequency standard values: guidelines and procedures. Metrologia 55, 188–200 (2018).

    ADS 

    Google Scholar
     

  • 7.

    Sanner, C. et al. Optical clock comparison for Lorentz symmetry testing. Nature 567, 204–208 (2019).

    ADS 

    Google Scholar
     

  • 8.

    Delva, P. et al. Test of special relativity using a fiber network of optical clocks. Phys. Rev. Lett. 118, 221102 (2017).

    ADS 

    Google Scholar
     

  • 9.

    Takamoto, M. et al. Test of general relativity by a pair of transportable optical lattice clocks. Nat. Photon. 14, 411–415 (2020).

    ADS 

    Google Scholar
     

  • 10.

    Godun, R. M. et al. Frequency ratio of two optical clock transitions in 171Yb+ and constraints on the time variation of fundamental constants. Phys. Rev. Lett. 113, 210801 (2014).

    ADS 

    Google Scholar
     

  • 11.

    Huntemann, N. et al. Improved limit on a temporal variation of mp/me from comparisons of Yb+ and Cs atomic clocks. Phys. Rev. Lett. 113, 210802 (2014).

    ADS 

    Google Scholar
     

  • 12.

    Delva, P., Denker, H. & Lion, G. in Relativistic Geodesy. Fundamental Theories of Physics 25–85 (eds Puetzfeld, D. & Lämmerzahl, C.) Vol. 196 (Springer, 2019).

  • 13.

    Grotti, J. et al. Geodesy and metrology with a transportable optical clock. Nat. Phys. 14, 437–441 (2018).


    Google Scholar
     

  • 14.

    Bondarescu, R. et al. Ground-based optical atomic clocks as a tool to monitor vertical surface motion. Geophys. J. Int. 202, 1770–1774 (2015).

    ADS 

    Google Scholar
     

  • 15.

    Derevianko, A. & Pospelov, M. Hunting for topological dark matter with atomic clocks. Nat. Phys. 10, 933–936 (2014).


    Google Scholar
     

  • 16.

    Kómár, P. et al. A quantum network of clocks. Nat. Phys. 10, 582–587 (2014).


    Google Scholar
     

  • 17.

    Kolkowitz, S. et al. Gravitational wave detection with optical lattice atomic clocks. Phys. Rev. D 94, 124043 (2016).

    ADS 

    Google Scholar
     

  • 18.

    Lisdat, C. et al. A clock network for geodesy and fundamental science. Nat. Commun. 7, 12443 (2016).

    ADS 

    Google Scholar
     

  • 19.

    Clivati, C. et al. Optical frequency transfer over submarine fiber links. Optica 5, 893–901 (2018).

    ADS 

    Google Scholar
     

  • 20.

    Hachisu, H. et al. Direct comparison of optical lattice clocks with an intercontinental baseline of 9,000 km. Opt. Lett. 39, 4072–4075 (2014).

    ADS 

    Google Scholar
     

  • 21.

    Riedel, F. et al. Direct comparisons of European primary and secondary frequency standards via satellite techniques. Metrologia 57, 045005 (2020).

    ADS 

    Google Scholar
     

  • 22.

    Fujieda, M. et al. Advanced satellite-based frequency transfer at the 10−16 level. IEEE Trans. Ultrasonics Ferroelectrics Frequency Control 65, 973–978 (2018).


    Google Scholar
     

  • 23.

    Leute, J. et al. Frequency comparison of 171Yb+ ion optical clocks at PTB and NPL via GPS PPP. IEEE Trans. Ultrasonics Ferroelectrics Frequency Control 63, 981–985 (2016).


    Google Scholar
     

  • 24.

    Event Horizon Telescope Collaboration First M87 event horizon telescope results. I. The shadow of the supermassive black hole. Astrophys. J. Lett. 875, L1 (2019).

    ADS 

    Google Scholar
     

  • 25.

    Schuh, H. & Behrend, D. VLBI: a fascinating technique for geodesy and astrometry. J. Geodynamics 61, 68–80 (2012).

    ADS 

    Google Scholar
     

  • 26.

    Coates, R. J. & Clark, T. A. Worldwide time and frequency synchronization by planned VLBI network. In Proc. Sixth Annual Precise Time and Time Interval (PTTI) Planning Meeting 361–371 (NASA, 1974).

  • 27.

    Clark, T. A. et al. Synchronization of clocks by very-long-baseline interferometry. IEEE Trans. Instrumentation Measurement 28, 184–187 (1979).

    ADS 

    Google Scholar
     

  • 28.

    Hobiger, T., Rieck, C., Haas, R. & Koyama, Y. Combining GPS and VLBI for inter-continental frequency transfer. Metrologia 52, 251–261 (2015).

    ADS 

    Google Scholar
     

  • 29.

    Koyama, Y. The use of very long baseline interferometry for time and frequency metrology. MAPAN J. Metrol. Soc. India 27, 23–30 (2012).


    Google Scholar
     

  • 30.

    Fey, A. L. et al. The second realization of the international celestial reference frame by very long baseline interferometry. Astron. J. 150, 58 (2015).

    ADS 

    Google Scholar
     

  • 31.

    Boehm, J., Werl, B. & Schuh, H. Troposphere mapping functions for GPS and very long baseline interferometry from European centre for medium-range weather forecasts operational analysis data. J. Geophys. Res. Solid Earth 111, B02406 (2006).

    ADS 

    Google Scholar
     

  • 32.

    Niell, A. et al. Demonstration of a broadband very long baseline interferometer system: a new instrument for high-precision space geodesy. Radio Sci. 53, 1269–1291 (2018).

    ADS 

    Google Scholar
     

  • 33.

    Kondo, T. & Takefuji, K. An algorithm of wideband bandwidth synthesis for geodetic VLBI. Radio Sci. 51, 1686–1702 (2016).

    ADS 

    Google Scholar
     

  • 34.

    Pizzocaro, M. et al. Absolute frequency measurement of the 1S03P0 transition of 171Yb with a link to international atomic time. Metrologia 57, 035007 (2020).

    ADS 

    Google Scholar
     

  • 35.

    Hachisu, H., Petit, G., Nakagawa, F., Hanado, Y. & Ido, T. SI-traceable measurement of an optical frequency at the low 1 × 10−16 level without a local primary standard. Opt. Express 25, 8511–8523 (2017).

    ADS 

    Google Scholar
     

  • 36.

    Hachisu, H., Nakagawa, F., Hanado, Y. & Ido, T. Months-long real-time generation of a time scale based on an optical clock. Sci. Rep. 8, 4243 (2018).

    ADS 

    Google Scholar
     

  • 37.

    Recommended Values of Standard Frequencies for Applications Including the Practical Realization of the Metre and Secondary Representations of the Definition of the Second (BIPM, accessed July 2020); https://www.bipm.org/en/publications/mises-en-pratique/standard-frequencies.html

  • 38.

    Takamoto, M. et al. Frequency ratios of Sr, Yb and Hg based optical lattice clocks and their applications. C. R. Phys. 16, 489–498 (2015).


    Google Scholar
     

  • 39.

    Nemitz, N. et al. Frequency ratio of Yb and Sr clocks with 5 × 10−17 uncertainty at 150 s averaging time. Nat. Photon. 10, 258–261 (2016).

    ADS 

    Google Scholar
     

  • 40.

    Udem, T., Holzwarth, R. & Hänsch, T. Femtosecond optical frequency combs. Eur. Phys. J. Special Topics 172, 69–79 (2009).

    ADS 

    Google Scholar
     

  • 41.

    Clivati, C. et al. A VLBI experiment using a remote atomic clock via a coherent fibre link. Sci. Rep. 7, 40992 (2017).

    ADS 

    Google Scholar
     

  • 42.

    Hachisu, H. & Ido, T. Intermittent optical frequency measurements to reduce the dead time uncertainty of frequency link. Jpn J. Appl. Phys. 54, 112401 (2015).

    ADS 

    Google Scholar
     

  • 43.

    Grebing, C. et al. Realization of a timescale with an accurate optical lattice clock. Optica 3, 563–569 (2016).

    ADS 

    Google Scholar
     

  • 44.

    Petit, G. et al. 1 × 10−16 frequency transfer by GPS PPP with integer ambiguity resolution. Metrologia 52, 301–309 (2015).

    ADS 

    Google Scholar
     

  • 45.

    Johnson, L. A. M., Gill, P. & Margolis, H. S. Evaluating the performance of the NPL femtosecond frequency combs: agreement at the 10−21 level. Metrologia 52, 62–71 (2015).

    ADS 

    Google Scholar
     

  • 46.

    Xu, M. H. et al. Structure effects for 3,417 celestial reference frame radio sources. Astrophys. J. Supplement Series 242, 5 (2019).

    ADS 

    Google Scholar
     

  • 47.

    Bolotin, S. et al. The source structure effect in broadband observations. In Proceedings of the 24th Meeting of the European VLBI Group for Geodesy and Astrometry 224–228 (CNIG, 2019).

  • 48.

    Riehle, F. Optical clock networks. Nat. Photon. 11, 25–31 (2017).

    ADS 

    Google Scholar
     

  • 49.

    Fujieda, M. et al. Carrier-phase two-way satellite frequency transfer over a very long baseline. Metrologia 51, 253–262 (2014).

    ADS 

    Google Scholar
     

  • 50.

    Laurent, P., Massonnet, D., Cacciapuoti, L. & Salomon, C. The ACES/PHARAO space mission. C. R. Phys. 16, 540–552 (2015).


    Google Scholar
     

  • 51.

    Clark, T. A. et al. Precision geodesy using the Mark-III very-long-baseline interferometer system. IEEE Trans. Geosci. Remote Sensing GE-23, 438–449 (1985).

    ADS 

    Google Scholar
     

  • 52.

    Sekido, M. et al. A broadband VLBI system using transportable stations for geodesy and metrology. J. Geodesy (in the press).

  • 53.

    Sekido, M. et al. An overview of the Japanese GALA-V wideband VLBI system. In International VLBI Service for Geodesy and Astrometry 2016 General Meeting Proc.New Horizons with VGOS’, NASA/CP-2016-219016 (eds Behrend, D., Baver, K. D. & Armstrong, K. L.) 25–33 (NASA, 2016).

  • 54.

    Ujihara, H., Takefuji, K., Sekido, M. & Ichikawa, R. Development of wideband antennas. In International Symposium on Advancing Geodesy in a Changing World (eds Freymueller, J. T. & Sánchez, L.) 25–28 (Springer, 2019).

  • 55.

    Takefuji, K. et al. High-order sampling techniques of aliased signals for very long baseline interferometry. Publ. Astron. Soc. Pacific 124, 1105–1112 (2012).

    ADS 

    Google Scholar
     

  • 56.

    Clark, T. A. Geodetic interferometry submission for the IUGG quadrennial report reviews of geophysics and space physics. Rev. Geophys. 17, 1430–1437 (1979).

    ADS 

    Google Scholar
     

  • 57.

    Hase, H., Bäer, A., Riepl, S. & Schlüter, W. Transportable integrated geodetic observatory (TIGO). In International VLBI Service for Geodesy and Astrometry 2000 General Meeting Proc. 383–387 (NASA, 2000).

  • 58.

    Xu, M. H. et al. The source structure of 0642 + 449 detected from the CONT14 observations. Astron. J. 152, 151 (2016).

    ADS 

    Google Scholar
     

  • 59.

    Kimura, M. Development of the software correlator for the VERA system III. International VLBI Service for Geodesy and Astrometry (IVS) National Institute of Information and Communications Technology (NICT) Technology Development Center News 29, 12–14 (2008).


    Google Scholar
     

  • 60.

    Gordon, D. et al. GSFC VLBI analysis center report. In International VLBI Service for Geodesy and Astrometry 2015+2016 Biennial Report (eds Baver, K. D., Behrend, D. & Armstrong, K. L.) NASA/TP-2017-219021 (NASA, 2017).

  • 61.

    Resolution B2 of the Thirtieth General Assembly of the IAU on the Third Realization of the International Celestial Reference Frame (IAU, 2018); https://www.iau.org/administration/resolutions/general_assemblies/

  • 62.

    Petit, G. & Luzum, B. IERS Conventions (2010) IERS Technical Note 36 (International Earth Rotation and Reference Systems Service, 2010).

  • 63.

    Saastamoinen, J. in The Use of Artificial Satellites for Geodesy 247–251 (eds Henriksen, S.W., Mancini, A., & Chovitz, B.H.) Vol. 15 (AGU, 2013).

  • 64.

    Landskron, D. & Böhm, J. VMF3/GPT3: refined discrete and empirical troposphere mapping functions. J. Geodesy 92, 349–360 (2018).

    ADS 

    Google Scholar
     

  • 65.

    Pizzocaro, M. et al. Absolute frequency measurement of the 1S03P0 transition of 171Yb. Metrologia 54, 102–112 (2017).

    ADS 

    Google Scholar
     

  • 66.

    Takamoto, M., Hong, F.-L., Higashi, R. & Katori, H. An optical lattice clock. Nature 435, 321–324 (2005).

    ADS 

    Google Scholar
     

  • 67.

    Sherman, J. A. et al. High-accuracy measurement of atomic polarizability in an optical lattice clock. Phys. Rev. Lett. 108, 153002 (2012).

    ADS 

    Google Scholar
     

  • 68.

    Middelmann, T., Falke, S., Lisdat, C. & Sterr, U. High accuracy correction of blackbody radiation shift in an optical lattice clock. Phys. Rev. Lett. 109, 263004 (2012).

    ADS 

    Google Scholar
     

  • 69.

    Nemitz, N., Jørgensen, A. A., Yanagimoto, R., Bregolin, F. & Katori, H. Modeling light shifts in optical lattice clocks. Phys. Rev. A 99, 033424 (2019).

    ADS 

    Google Scholar
     

  • 70.

    Brown, R. C. et al. Hyperpolarizability and operational magic wavelength in an optical lattice clock. Phys. Rev. Lett. 119, 253001 (2017).

    ADS 

    Google Scholar
     

  • 71.

    Westergaard, P. G. et al. Lattice-induced frequency shifts in Sr optical lattice clocks at the 10−17 level. Phys. Rev. Lett. 106, 210801 (2011).

    ADS 

    Google Scholar
     

  • 72.

    Nicholson, T. et al. Systematic evaluation of an atomic clock at 2 × 10−18 total uncertainty. Nat. Commun. 6, 6896 (2015).

    ADS 

    Google Scholar
     

  • 73.

    Gibble, K. Scattering of cold-atom coherences by hot atoms: frequency shifts from background-gas collisions. Phys. Rev. Lett. 110, 180802 (2013).

    ADS 

    Google Scholar
     

  • 74.

    Baillard, X. et al. Accuracy evaluation of an optical lattice clock with bosonic atoms. Opt. Lett. 32, 1812–1814 (2007).

    ADS 

    Google Scholar
     

  • 75.

    On the definition of time scales. In Resolutions Adopted; 26th General Conference on Weights and Measures (CGPM) Resolution 2 (BIPM, 2018); https://www.bipm.org/en/cgpm-2018/

  • 76.

    Denker, H. et al. Geodetic methods to determine the relativistic redshift at the level of 10−18 in the context of international timescales: a review and practical results. J. Geodesy 92, 487–516 (2018).

    ADS 

    Google Scholar
     

  • 77.

    Miyahara, B., Kodama, T. & Kuroishi, Y. Development of new hybrid geoid model for Japan, ‘GSIGEO2011’. Bull. Geosp. Inform. Auth. Jpn 62, 11–20 (2014).


    Google Scholar
     

  • 78.

    Clivati, C. et al. A coherent fiber link for very long baseline interferometry. IEEE Trans. Ultrasonics Ferroelectrics Frequency Control 62, 1907–1912 (2015).


    Google Scholar
     

  • 79.

    Barbieri, P., Clivati, C., Pizzocaro, M., Levi, F. & Calonico, D. Spectral purity transfer with 5 × 10−17 instability at 1 s using a multibranch Er:fiber frequency comb. Metrologia 56, 045008 (2019).

    ADS 

    Google Scholar
     

  • 80.

    Yu, D.-H., Weiss, M. & Parker, T. E. Uncertainty of a frequency comparison with distributed dead time and measurement interval offset. Metrologia 44, 91–96 (2007).

    ADS 

    Google Scholar
     

  • 81.

    Riley, W. J. Handbook of Frequency Stability Analysis. NIST Special Publication 1065 (National Institute of Standards and Technology, 2008).

  • 82.

    Kasdin, N. J. & Walter, T. Discrete simulation of power law noise (for oscillator stability evaluation). In Proceedings of the 1992 IEEE Frequency Control Symposium 274–283 (IEEE, 1992).

  • 83.

    Nakagawa, F., Imae, M., Hanado, Y. & Aida, M. Development of multichannel dual-mixer time difference system to generate UTC(NICT). IEEE Trans. Instrumentation Measurement 54, 829–832 (2005).


    Google Scholar
     

  • 84.

    Luenberger, D. G. Optimization by Vector Space Methods (Wiley, 1998).

  • 85.

    Margolis, H. S. & Gill, P. Least-squares analysis of clock frequency comparison data to deduce optimized frequency and frequency ratio values. Metrologia 52, 628–634 (2015).

    ADS 

    Google Scholar